The deterioration of underground pipelines in industrial and municipal settings is an infrastructure illness that continually grows due to a wide range of harmful influences. For example, chemical wastes, root intrusion, abrasive substances, earthquakes and flooding all have a corrosive effect on underground pipeline systems that causes leakage and infiltration and threatens our environment.
Recent federal and state laws have mandated that all industrial waste pipelines must be replaced with dual-containment pipe or that a leak detection system must be installed and activated on each line section. Insofar as there is no cost-effective leak detection system that can be implemented for an existing single-containment pipeline, the only solution is to install a dual-containment pipeline. A dual-containment pipeline consists of an outer pipe and an inner pipe having a diameter less than the outer pipe and being centered therein. An equal annular space is provided between the pipes to allow any flow outside of the inner pipe to be detected immediately.
Re-laying an entire new network of either single- or double-containment pipes to replace existing pipelines is not a feasible solution for overcoming the problems associated with corroded or defective pipelines because it is costly, disruptive and slow. The cost of excavation alone in most industrial areas is excessive due to the contaminated soil surrounding the existing pipelines. Further, it is desirable to minimize destruction of surface features so as not to disturb local residences, businesses and utilities. Therefore, there is a need in the art to establish a quick and inexpensive, no dig solution for rehabilitating existing pipelines and for converting single-containment pipelines to a dual-containment system.
Reconstructing defective pipelines in situ by inserting a lining pipe therein and leaving no annular space therebetween is the preferred method for overcoming the above-identified problems. However, known relining methods cannot accommodate the diversity of pipeline materials and non-standardized diameters presently used. Typical pipelines comprise such materials as vitrified clay, reinforced concrete, cast iron, ductile iron, asbestos, cement, steel or even hollow logs. Reconstruction costs therefore vary depending upon pipeline size, composition and location.
Lining existing pipelines in situ with inner pipes having a non-cylindrical shape is known in the prior art. Tight-fitting pipe lining inserts are conventionally used to enhance a pipeline's strength. Typical methods for lining pipelines include the steps of forming flexible piping or tubing (e.g. polyethylene) having a fold therein at an extrusion plant, holding the tube in this folded state, inserting the deformed tube into existing pipelines and releasing the tube so that it returns to its original cylindrical form. As representative of such art, reference may be had to U.S. Pat. No. 3,894,328 to Jansson. Known lining pipes are typically produced at high temperatures having a U-shape, rather than being extruded in cylindrical form and then being deformed to a reduced diameter. This increases relining costs because of the necessity for special extrusion equipment and for high energy to reform the pipe after insertion into an existing pipeline.
The prior art also shows deforming lining pipes at the site of a host pipe for insertion therein. For example, U.S. Pat. No. 5,091,137 to Ledoux discloses deforming a thermoplastic extrudate (i.e. a lining pipe) into a U-shape to facilitate insertion into the pipe to be lined. In FIG. 1 of the patent, the deforming apparatus comprises a pair of fixed positioning rollers 14 and 16 located perpendicular to one another and a pair of adjustable positioning rollers 18 and 20 also located perpendicular to one another, and opposite rollers 14 and 16. The thermoplastic extrudate is deformed by applying heat and passing it through a motor-driven deforming or penetration wheel. When fully inserted, the lining pipe is pressurized and heated to return the pipe to its original round shape.
U.S. Pat. No. 4,207,130 to Barber shows a method of lining pipes including the steps of extruding the lining pipe on site, deflecting the pipe, holding the pipe in its deflected state, feeding the deflected pipe into a host pipe and releasing the hold on the pipe so that it returns to its original form. The deforming apparatus has a deflecting roller carried by a frame and folding rollers. A plastic extrudate passes through a cold water spray to set the plastic material. The deflecting roller then deflects the upper central portion of the tube so that it takes up a horseshoe type configuration and rollers press the sides of the horseshoe cross section together. The lining pipe is propelled through the forming apparatus by a motor driven roller.
Another approach of the art is exemplified by U.S. Pat. Nos. 5,114,634 and 5,256,342 to McMillan et al. which show reducing the diameter of a lining for insertion into a host pipe by passing an elastomeric liner pipe through five sets of rollers. Each of the five sets of rollers defines a 360 degree region of contact with the liner and provides a progressively smaller liner-receiving opening to reduce the diameter of the lining pipe.